hfaxd: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/sbin/hfaxd - from package: hylafax+

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/hfaxd - from package: hylafax-server

You may install the required package with command apt-get install {package}

Error in other languages:
hfaxd: bevel nie gevind nie
hfaxd: comandă negăsită
hfaxd: comando não encontrado
hfaxd: commande introuvable
hfaxd: command not found
hfaxd: käsku ei ole
hfaxd: không tìm thấy lệnh
hfaxd: komanda nerasta
hfaxd: Kommando nicht gefunden.
hfaxd: kommandot finns inte
hfaxd: komut yok
hfaxd: nie znaleziono polecenia
hfaxd: níor aimsíodh an t-ordú
hfaxd: no se encontró la orden
hfaxd: no s'ha trobat l'ordre
hfaxd: opdracht niet gevonden
hfaxd: parancs nem található
hfaxd: perintah tidak ditemukan
hfaxd: príkaz nenájdený
hfaxd: příkaz nenalezen
hfaxd: команда не найдена
hfaxd: командата не е открита
hfaxd: 命令找不到
hfaxd: コマンドが見つかりません